Many physiological processes are characterized by the generation and propagation of multiple, dynamic and often transient electrical phenomena from the respective tissues and organs where they originate. The purpose of recording physiological signals is to obtain a record which is an exact facsimile of the events under investigation. However, it is seldom feasible to attach pickup elements directly to the tissues or organs being investigated, and some method of sensing the electrical phenomena from the surface of the body is usually employed. Such methods introduce measurement errors that result in a distorted picture of the processes being recorded. In spite of this limitation, these techniques have proven to be highly useful for the medical profession.
A wide variety of pickup elements of various sophistication have been developed and are presently available for recording many important phenomena associated with various physiological function from different anatomical sites. The important requirements for sensing electrodes and transducers presently employed in electrophysiological monitoring and recording are: (a) attachment to the body must result in a minimum of discomfort and movement restriction; (b) once applied, they should maintain their operation status without deterioration for extended periods of time; (c) avoid the necessity for reapplication and/or relocation; and (d) they must allow for a far greater degree of subject movement than usually prevails in clinical investigations.
Although a great deal of effort has already been spent in reducing the weight and size of electrodes and transducers, and in minimizing the adverse effects that occur over prolonged time periods, the present state of the art is far from ideal.
The methods employed for applying even simple bioelectric pickup electrodes in many instances is quite traumatic, as they require abrasion and debridement of the superficial keratinized skin layers. Such procedures frequently cause discomfort, and many contribute to the cause of skin reactions when electrodes are left applied to the same locations for many hours or days. The following scientific studies published in scientific and medical Journals are indicative of previous efforts in remotely recording electromagnetic fields that correspond to internal physiological processes of biological organisms without the use of any intermediary materials or electrodes attached to the skin:
(1) Burr, H. S., and Northrop, F., "The Electrodynamic Theory of Life", Quarterly Review of Biol., 1935, 10:322 PA1 (2) Burr, H. S., and Northrop, F., "Evidence For The Existence Of An Electrodynamic Field In Living Organisms", National Academy of Sciences, 1939, 25:284 PA1 (3) Burr, H. S., and Maure, A., "Electrostatic Fields of Sciatic Nerve In The Frog", Yale J. of Bio. Med., 1949, 21:455 PA1 (4) Seipell, H., and Morrow, R., "The Magnetic Field Accompanying Neuronal Activity Of The Nervous System", J. Wash. Acad. Sci., 1960, 50:1 PA1 (5) Cohen, D., "Magnetoencephalography: Evidence Of Magnetic Fields Produced By Alpha-Rhythm Currents", Science, 1968, 161:784 PA1 (6) Cohen, D., "Magnetoencephalography: Detection Of Brain's Electrical Activity With A Superconducting Magnetometer", Science, 1972, 175:664 PA1 (7) Cohen, D., "Magnetic Fields Of The Human Body", Physics Today, Aug. 1975, pp. 34-43 PA1 (8) Gulyaev, P. I., Zabotin, V. L. & Shippenbakh, N.Y., "The Electroauragram Of The Frog's Nerve, Muscle, Heart And Of The Human Heart And Musculature", Doklady Biological Science, 1968, 180, pp. 359-361 PA1 (9) Gulyaev, P. I., "The Electroauragram: The Electric Field Of Organisms As A New Biological Connection", Proceedings Of Symposium On Physics And Biology, Moscow, 1967, p. 19 PA1 (10) Goodman, D. A. and Weinberger, N. M., "Remote Sensing Of Behavior In Aquatic Amphibia Especially In Necturus Maculosus, The Mud Puppy", Comm. Behavioral Biology, 1971, 6, pp. 67-70 PA1 (11) Goodman, D. A. and Weinberger, N. M., "Submerged Electrodes In An Aquarium: Validation Of A Technique For Remote Sensing Of Behavior", Behav. Res. Meth. & Instru., 1971 3:6, pp. 281-286
Other devices have eliminated the necessity of topically connecting electromagnetic sensors to a person's skin. Some of these devices are described in U. S. Pat. Nos. 3,980,076 (Wikswo et al), 4,079,730 (Wikswo et al) and 4,444,199 (Shafer). However, these devices are not totally remote in that they will not operate through the ambient atmosphere from up to 12 feet away. Similarly, there have been problems in measuring the EKG, EEG, EMG, EOG and respiration in the super-low frequency (SLF) and extremely-low frequency (ELF) range of 0.3 to 40 Hertz. Thus, there exists a need for the development of physiological monitoring methods and equipment that do not require direct contact with the subject's integument (skin layer), and thus relieve the subjects from annoyance and encumbrance of bodily attachments.